Ximing Zhang,Yin Liu,Zhenying Liu,Yanfen Wang,Yueqing Wang,Ling Bing Kong
Ni x Zn (1-x) Fe 2 O 4 (x = 0.4, 0.6, 0.7, 1) nanocrystalline powders were synthesized by using a modified spraying-coprecipitation method. The spraying-coprecipitated precursors of Ni x Zn (1-x) Fe 2 O 4 were heated to form ferrites with different particle sizes. The particle size of the Ni x Zn (1-x) Fe 2 O 4 powders gradually decreased with increasing content of Ni. Due to small size effect and orientation polarization, the sample Ni 0.7 Zn 0.3 Fe 2 O 4 exhibited an RL min of −64.37 dB at 6.48 GHz, as the thickness was 5.91 mm. Meanwhile, it had an effective absorption frequency range of 3.6 – 7.44 GHz and a bandwidth of 3.84 GHz, covering almost the C-band. Therefore, the Ni x Zn (1-x) Fe 2 O 4 powders synthesized in this way are promising microwave absorbing materials.
To achieve non-invasive diabetes diagnosis through breath analysis, it is of great significance to construct a metal oxide acetone gas sensor with high sensitivity, selectivity and a low detection limit. Utilizing spinel ferrite materials with matching crystal structures to form high-quality heterojunctions can significantly enhance metal oxide sensing performance. Herein, a feasible strategy for constructing heterojunction composites using lattice-matched metal oxides, specifically inverse spinel NiFe 2 O 4 and normal spinel ZnFe 2 O 4 , was proposed to enhance the catalytic activity of acetone oxidation. By substituting Zn into NiFe 2 O 4 at the A-site and adjusting the Ni/Zn molar ratio, the synergistic effect of the heterojunction could be successfully implemented to enhance the detection of acetone. Notably, the optimal Ni 0.6 Zn 0.4 Fe 2 O 4 sensor exhibited remarkable acetone-sensing performance with a high response of 13.77 at 1 ppm, a detection limit as low as 20 ppb (theoretically as low as 171 ppt), strong humidity adaptability, a fast response time of 17 s at 1 ppm, exceptional selectivity, and long-term stability. In practical applications, the Ni 0.6 Zn 0.4 Fe 2 O 4 sensor was able to distinguished between acetone levels in the breath of healthy individuals and simulated diabetes patients, thereby suggesting their potential for auxiliary diabetes diagnosis. The results imply that normal/inverse spinel ferrite heterojunction composites could offer a novel strategy for effective acetone detection in breath analysis for the diagnosis of diabetes.
A simple hydrothermal method combined with microwave irradiation was used to synthesize nickel-zinc ferrite/coal-based carbon (Ni 1−x Zn x Fe 2 O 4 /CBC) composites. The influences of Zn 2+ concentration on the magnetism and microwave absorption characteristics of Ni 1−x Zn x Fe 2 O 4 /coal-based carbon composites were examined. The Ni 1−x Zn x Fe 2 O 4 particles were equally anchored on the coal-based carbon within the Ni 1−x Zn x Fe 2 O 4 /CBC composites. The dielectric and magnetism characteristics of Ni 1−x Zn x Fe 2 O 4 /CBC composites can be improved simultaneously by adjusting the Zn 2+ concentration. The minimum reflection loss (RLmin) for the sample at x = 0.4 is −65.5 dB for a thickness of 4.0 mm. The samples also have typical soft magnetic properties . Furthermore, some possible mechanisms of microwave absorption are investigated. Our Ni 1−x Zn x Fe 2 O 4 /CBC composites show great potential for microwave absorption applications.
危险品化学品经营许可证（带存储）